Lubrication Systems

Question 1

What is the likely cause of excessive oil consumption in a reciprocating engine without evidence of oil leaks?

Answer 1

Piston rings are worn or broken.

Question 2

What are the functions of lubricating oil in reciprocating engines?

Answer 2

Reduce friction between moving parts and remove heat.

Question 3

Name two important characteristics of aircraft engine oil.

Answer 3

Must be light enough to circulate freely but heavy enough to provide proper oil film at operating temperatures.

Question 4

What could happen to oil that is too low in viscosity at normal engine operating temperatures?

Answer 4

Could become so thin that the oil film between moving parts is easily broken resulting in premature wear.

Question 5

What factors must be considered by an engine manufacturer in determining the proper grade of oil for a particular engine?

Answer 5

Operating load, temperature, rotational speed.

Question 6

Why do aircraft reciprocating engines use relatively high viscosity oil?

Answer 6

Large operating clearances, high temperatures, high pressures.

Question 7

Name some oil contaminants.

Answer 7

Metal particles, dirt, carbon, moisture, acids.

Question 8

What is a possible indication of low oil pressure together with high oil temperature?

Answer 8

Low or inadequate oil supply.

Question 9

In ashless dispersant oils, what function does the dispersant perform?

Answer 9

Causes sludge forming materials to repel each other and remain suspended until trapped by oil filter or drained keeping oil passages and ring grooves free from harmful deposits and inside of engine clean.

Question 10

Why do oil reservoirs have expansion space?

Answer 10

For oil foaming, thermal expansion, air in the returned oil.

Question 11

What could cause oil foaming?

Answer 11

Diluted oil, contaminated oil, oil level being too high.

Question 12

What controls oil pressure in a gear type oil pressure pump?

Answer 12

Oil pressure relief valve.

Question 13

What function does an oil cooler bypass valve perform?

Answer 13

Direct oil through or around cooler to obtain proper operating oil temperatures.

Question 14

What could be a possible indication if the oil cooler passage becomes obstructed?

Answer 14

High oil temperature.

Question 15

Where is the oil temperature bulb usually located?

Answer 15

Engine oil inlet.

Question 16

What does the presence of metal particles in an engine oil filter indicate?

Answer 16

Depending on type and size of metal particles, usually indicates abnormal wear and possible internal failure.

Question 17

What should be done if metal particles are found in the engine oil filter?

Answer 17

Follow engine manufacturer’s maintenance instructions.

Question 18

Where is the most critical point of lubrication in a gas turbine engine?

Answer 18

At turbine bearing.

Question 19

What type of oil is used in a turbine engine oil system?

Answer 19

Synthetic oil.

Question 20

Where are oil screens or filters most likely located in a turbine engine oil system?

Answer 20

Oil pressure system main filter, scavenge system, at or just before oil jet.

Question 21

Name two types of turbine engine oil coolers.

Answer 21

Air cooled, fuel cooled.